Originally posted by mee I would like to see 1:1 crops taken from a 24 MP APS-C camera and another crop from a 24 MP FF camera each using a similarly rated lens with equivalent FL and aperture. Is the detail in the FF noticeable? negligible?
I had done some test shots in the past comparing how resolution and the effects of cropping to gain reach and then compared it to using a camera with less photosites but increasing the FL to the achieve the same FOV as cropping.
For the testing I used a pentax 16mp K5 and compared it to the pentax 6mp DS. I used these 2 cameras as they are very close to ratio of photosite size that we see between FF and cropped. When the K5 is cropped by a factor of 1.6 we wind up with a resulting image that is 6mp.
One of the first test I had performed was as direct comparison of the same lens at the same F-stop and holding the framing as to hold the size of the subject within the frame. This was done by moving the camera closer to the subject by the crop factor.
Many would suspect that the relatively large photo sites of the K5 and the DS that it should not be hard for the DFA to resolve more than enough detail for you not to lose any resolution when cropping but this shows the opposite. As photosites get smaller the gap start to become more noticeable than this.
As we decrease the size of the photo sites to increase the captured resolution of both the camera and lens we only grain a fraction of that increase in pixel density, this is why we lose resolution via cropping
When cropped we need to enlarge the image circle projected by the lens by the factor that we have cropped. This shows more of the lenses faults, to combat this the lens that is being cropped has to resolve more to make up this. This also means that for the larger format you can use a lens that resolves less while still retaining the same final resolution in the image.
I don’t have a 150mm prime lens the same caliber as the DFA100mm so I went into my box of lenses and dug out and found an old M 80-200F4.5. Here you can see that with the larger photo sites of the DS when shot at the same FOV and DOF we are able to resolve the same level of detail ( maybe more)as camera with smaller photo sites using a prime lens.
Here was other test that I have done using the same cameras and the same cropping as above, the only difference was I used the sigma 70-200 F2.8 on the DS. Again they are shot at the same DOF and FOV to mimic FF to cropped
I had used a slanted target to avoid any focusing errors ( click to view at 100%)
Image resources also conducted resolution testing
They show the same findings
Click to view at 100%